1. Field of the Invention
The present invention relates to a service system for transmitting information about a calling subscriber to a called subscriber terminal that is accommodated in an access network.
2. Related Arts
In a switch system, a service for transmitting the phone number, etc., of a calling subscriber to a called subscriber has been standardized, when the service is provided using ISDN. Also proposed for an analog subscriber is a function to notify a called subscriber of the phone number of a calling subscriber, between call rings, that would be included in a subscriber circuit.
Although the function of the access network was with a local exchange, since there are a variety of subscriber terminals and since there is a long distance between a subscriber terminal and a local exchange, it has been proposed that the access network be established independent of the local exchange. In this case, an interface would be required for communication between an independent access network and a local exchange, and an interface (V5) is being adopted as a standard for this purpose.
The standard interface (V5) is specified by the ETSI in Europe, and further, has been designated as the international standard by the International Telecommunication Union (ITU).
In addition the standard interface (V5) is advantageous in that a network user (PTT) can reduce a selection range for an access network and the time required for building a network, because the interface between the local exchange and the access network, by which subscriber terminals are accommodated, is standardized.
The network user (PTT), therefore, voluntarily adopts the standard interface (V5). In this case, however, no provision is made for the acceptance of a service for notifying a called subscriber of the phone number of a calling subscriber, so that a called subscriber can not avail him or herself of the caller phone number service.
Recently, wireless terminals, such as a portable telephones, have been popular as subscriber terminals. When a wireless terminal is to be accommodated by an access network, the interface function for the wireless terminal has a different configuration than that interface function that is used with a wire connection for accommodating a subscriber terminal on the access network.
Therefore, conventionally, the protocol that is employed differs depending on whether a subscriber terminal accommodated by the access network is an analog subscriber terminal or is an ISDN terminal, and whether the access network and the subscriber terminal are connected by wire or by wireless.
In particular, the protocol is undetermined that is to be used when the subscriber terminal that is accommodated by the access network is an analog subscriber terminal that is connected to the access network by wireless.